There is known a non-patent document as described below as a standard of 6LoWPAN (IPv6 over Low-Power Wireless Personal Area Networks). The 6LoWPAN allows IPv6 to be used over IEEE 802.15.4.
Home area networks using the 6LoWPAN have been recently considered. Here, users' houses are sometimes equipped with a plurality of networks such as a home energy management system (HEMS) and a smart meter. When a plurality of networks are equipped, a plurality of wireless devices serving as edge routers are also present. For example, in a case where a HEMS is introduced into a house preliminarily equipped with a smart meter, the house is to be installed with two wireless devices, which are the smart meter and a HEMS controller, each serving as an edge router.
When a plurality of wireless devices each serving as an edge router are equipped as described above, HEMS terminals such as an air conditioner and a heat pump composing the HEMS are each assigned with a plurality of IPv6 addresses.